A high level cleric/thief can use a sword (Use Any Item HLA) but (s)he will remain non-proficient though. Probably not what you are looking for unless you have a very specific dual wielding build in mind.
Of course, unless a Cleric/Thief is a dual-classed Human, you won't be able to spend proficiency points in bladed weapons, which results in a penalty on attack rolls using them. This penalty is not exactly negligible considering the THAC0 progression of Clerics compared to warrior classes.
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Also, in BG2 if you're a paladin you begin to get divine spells, so maybe such a character can serve as a cleric with swords for you.
Probably not what you are looking for unless you have a very specific dual wielding build in mind.
Maybe one day, we will get that (kit).